Each year there are an increasing number of cars on roads，as millions of new cars are produced．One out of every six Americans works at putting together the parts of cars，driving trucks，building roads or filling cars with gas．Americans couldn't live without cars!

Most Americans find it hard to think what life would be without a car．However，some have realized the serious problem caused by cars．The polluted air is harmful and dangerous to health．

One way to get rid of the polluted air is to design a new car．That is what several large car factories are trying to do．But to build the new car is easier said than done．Progress in this field has been slow．

Another way is to replace the car engine with something else．Engineers are working on some new cars．Many makers believe that it will take years to develop a practical model that pleases people．

To prevent the world from being polluted by cars，we'll have to make some changes．Americans，for example，have to cut down the number of their cars．They are encouraged  to travel and go to work by bike．Riding a bike is thought to help keep the air clean．

But this change does not come easily．A large number of workers may find themselves with no jobs if a car factory closes down．And the problem of air would become less important than that of unemployment．

Although ears have brought us a better life，they have also brought us new problems．

1．Some large car factories in the U．S．A are trying to make a new kind of car which _______．

A．is clean in itself                                 B．is used to clean streets

C．is easier to make                                       D．does not pollute the air

2．If the number of cars is cut down，the most serious problem to American workers is to _____．

A．lose their jobs                                          B．pollute their environment

C．go to work on foot                                  D．make their factories richer

3．The writer wants to tell us that _________．

A．riding a bike is the only way out

B．the number of caps must be cut down

C．people wouldn't live without cars

D．cars bring us not only a better life，but also serious problems

4．Which fact does the passage provide?

A．About one sixth of American workers are working in car factories．

B．The hest way to get rid of air pollution is to change the car engine for something else．

C．It isn't easy to change the way of life in the U．S．A．

D．In the U．S．A，bikes will surely take the place of cars in the future．

5．Which is the best title for the passage?

A．A New way to Get Rid of Polluted Air             B．Cars and Polluted Air

C．Many Serious Problems in the U．S．A         D．Changes in Car Production